'non-disclosable' originates from the negative prefix 'non-' (from Latin 'non', meaning 'not') combined with 'disclosable' (formed from the verb 'disclose' + the adjectival suffix '-able').

'disclose' comes into English via Old French 'desclore' (from Latin elements including 'dis-' + a root related to 'claudere'/'clausum' meaning 'to close'), developed in Middle English as 'disclosen'/'disclose', and '-able' is a productive English suffix meaning 'capable of'. The modern compound 'non-disclosable' is a recent English formation created by adding 'non-' to 'disclosable'.

Originally 'disclose' meant 'to uncover or open up' and later took on the sense 'to make known'; 'disclosable' came to mean 'able to be made known', and adding 'non-' gives the current meaning 'not able to be made known or revealed'.